The field of the present invention relates to sprinklers. More particularly, it relates to the type of sprinkler which has an arm which is rotated into and out of a stream of water.
In the past, rotatable impact sprinklers have been manufactured with elongated members functioning as rotatable arms. A rotatable arm has been equipped with a spoon for channeling water. Incoming water from the nozzle hits an incoming ramp at the incoming end of the spoon. The water goes through a window to hit a reaction surface on the other side of the spoon toward the exit end of the spoon. Such an arm has been attached to a sprinkler body, or housing, on a fulcrum pin with a spring which pushes such arm into an incoming stream coming from a sprinkler nozzle. The force of the stream on the spoon pushes the arm back out of the stream, and the spring repeatedly pushes it back into the stream. In this way, the prior art has attempted to spread the water entering a sprinkler over a circular or pie shaped range.
However, it has been a difficult problem in the sprinkler industry to provide sufficient water near the sprinkler ("enclosed water"). Such sprinklers have distributed an undesirable high portion of incoming water to outer bands of its far ranges. A sprinkler of any prior design has left a "brown spot" in the area less than ten feet from the sprinkler due to lack of enclosed water. The problem of brown spots receiving too little enclosed water is exacerbated by the usual practice of overlapping neighboring sprinklers by about one-third their maximum radius. Overlap is needed to fill in gaps between circular sprinkler distribution patterns, but it nearly doubles the already too-high proportion of water in the outer third of each sprinkler distribution.
Various approaches have been attempted in the past to provide more enclosed water with such a sprinkler while attempting to maintain a wide range with maximal outer distance of water thrown. All of these approaches have interfered with the maximum distance which water is thrown by a "cannon shot" of a stream when the arm is not interrupting the stream.
A first prior approach has been to permanently extend a pin from the sprinkler body. Such a pin can be screwed through an extender further into or out of the stream. Since such a pin, once adjusted, is always in the stream, it interferes with maximum cannon shot projection. It also requires adjustment of each sprinkler.
A second prior approach has been to replace the pin of the first approach with a shield. Such a shield can be rotated in an out of the stream. Like the pin of the first approach, a shield is always in the same place once adjusted, and therefore interferes with maximum cannon shot projection. It too has to be adjusted for each sprinkler. A third approach has been the "controlled droplet size" (CDS) approach. CDS has been accomplished with a trapezoidal-shaped nozzle which changes the stream to a more general spray. There are many problems with CDS. CDS cuts down on the range because it causes interfering forces within an exiting spray. CDS nozzles cause more spilling outside of the spoon because the spray is wider and some water misses the spoon. Such spilling causes puddling at the base of the sprinkler. A CDS spray applies less force to the spoon because it is wider and spills more. With less force on the spoon, the arm is more likely to "hang up" by oscillating back and forth (usually less than one-eighth of an inch) in the incoming spray when there is insufficient force to push the spoon back out of the spray to permit a cannon shot.
A fourth approach has been to install a second nozzle in the sprinkler. Such a second nozzle however, requires more pressure to adequately drive an arm in and out of the first nozzle's stream. Diversion of water to a second nozzle can also cut down on the maximum cannon shot projection of the sprinkler. Most homes lack the pressure required to make such a sprinkler work properly. Most homes have 25 p.s.i. or less water pressure, whereas a second nozzle generally demands more than this.
A fifth approach has been to cut groove into the nozzle. This suffers from most of the problems of the CDS system discussed above.